Dispersed laser-induced fluorescence of molecular ions. Identification of new low-lying electronic states of TiCl+ and TiF+ Original Research Article

The dispersed laser-induced fluorescence technique has been applied for the first time to metallic molecular ions. The TiCl+ and TiF+ ions were produced by a high-voltage discharge in helium with traces of TiCl4 or TiF4. A c.w. dye-laser and a grating plate spectrometer were used to record low-resolution spectra of these species in the visible. This leads to the observation of new low-lying electronic states of these ions: the C3Π (∼1535 cm−1) state of TiCl+, the B3Δ (∼2040 cm−1) and C3Π (∼2200 cm−1) states of TiF+. The identification of these new states contributes to a better characterisation of the first 3000 cm−1 of the energy level diagrams of these molecules. The experimental position of the C3Π state of TiCl+ is in good agreement with theoretical predictions given by a Ligand Field Theory model [C. Focsa, M. Bencheikh, L.G.M. Pettersson, J. Phys. B: At. Mol. Opt. Phys. 31 (1998) 2857]. We have extended these calculations to the TiF+ isovalent ion, taking advantage of the new experimental data. Both experimental and theoretical new results presented in this paper are expected to help future investigations on these species.